title: A case of sulphasalazine potentiating the hypoprothombinemic effect of warfarin resulting in bleeding.
abstract: OBJECTIVE
  One case report demonstrated warfarin resistance associated with sulphasalazine therapy. Our objective is to report on a case of warfarin potentiation rather than resistance, associated with sulphasalazine therapy.
  
  
  METHODS
  The patient was taking warfarin for two mechanical heart valves and was prescribed sulphasalazine for inflammatory bowel disease. He had stable international normalized ratios (INRs) before sulphasalazine administration. Approximately 3 weeks after starting sulphasalazine, he presented to the anticoagulation clinic with bruising and an INR of 6·1. The sulphasalazine was stopped, and the warfarin was held for 3 days; then the previous dose was resumed. Three weeks later, the INR returned to a therapeutic level.
  
  
  CONCLUSIONS
  This is the first case of sulphasalazine potentiating the effect of warfarin. Sulphasalazine may potentiate the hypoprothombinemic effect of warfarin.
authors.affiliation: College of Pharmacy, Tucson, AZ, USA.
authors.forename: S
authors.initials: S
authors.lastname: Hall
authors.forename: J P
authors.initials: JP
authors.lastname: Rindone
mesh_terms: D000554:Ambulatory Care Facilities; D000925:Anticoagulants / Q000009:adverse effects* / Q000493:pharmacokinetics* / Q000627:therapeutic use; D004357:Drug Synergism; D005765:Gastrointestinal Agents / Q000493:pharmacokinetics / Q000627:therapeutic use; D006470:Hemorrhage / Q000139:chemically induced*; D006801:Humans; D007020:Hypoprothrombinemias / Q000139:chemically induced; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D012460:Sulfasalazine / Q000493:pharmacokinetics / Q000627:therapeutic use*; D014859:Warfarin / Q000009:adverse effects* / Q000493:pharmacokinetics* / Q000627:therapeutic use
chemical_list: D000925:Anticoagulants; D005765:Gastrointestinal Agents; D012460:Sulfasalazine; D014859:Warfarin